This invention relates to the processes and systems for the treatment and minimization of waste, and more specifically to a biological treatment unit utilizing a tolerant and effective mixture of cannibalizing microorganisms for the enhanced treatment and degradation of organic wastes to inert levels. The wastes, which are generated from plants, including petroleum oil refineries, petrochemical and chemical processing facilities, municipal wastewater treatment plants and other industrial operations, and from such plant's associated wastewater treatment facilities, are treated in accordance with the novel process and system disclosed herein, resulting in the minimization of such wastes. In particular, use of the invention disclosed herein has generated the unexpected result that little, or no, solids are required to be removed during normal operating conditions.
Under the federal Resource Conservation and Recovery Act, amended by the Hazardous and Solid Waste Amendments of 1984, 42 United States Code 6901 et. seq, (RCRA), and subsequent regulations, 40 Code of Federal Regulations 261 et. seq., all of which are incorporated by reference (the United States Code shall hereunder by referred to as "USC" and the Code of Federal Regulations shall hereunder be referred to as "CFR"), the U.S. Environmental Protection Agency (EPA) identified wastes that would be classified as "hazardous" through either a specific listing ("listed" wastes) or through characteristics of toxicity, corrosivity, ignitability, or reactivity ("characteristic" wastes). For example, Dissolved Air Flotation (DAF) sludge or float, and American Petroleum Institute (API) Separator sludge, by-products of traditional oil refinery wastewater treatment trains, are each "listed" by the EPA as a waste from a specific source, and thus a hazardous waste by definition. See e.g. 40 CFR 261.31 and 261.32, all of which are herein incorporated by reference. Other listed petroleum refining wastes from specific sources include slop oil emulsion solids, heat exchanger bundle cleaning sludge and tank bottoms. Petroleum refinery wastes from non-specific sources include primary (gravitational) oil/water/solids separation sludge and secondary (emulsified) oil/water/solids separation sludges. Id. Dissolved Gas Flotation units are sometimes used instead of DAF units for the same purposes when a non-combustible gas is required for flotation. (For simplicity, the term "DAF", as hereinafter used, shall mean both Dissolved Air Flotation and Dissolved Gas Flotation.)
DAF, API Separator and similar treatment units may also be found in other industrial facilities, such as those producing or utilizing chemicals, petrochemicals, polymers, rubbers, pesticides, oil and gas, hydrocarbon, synthetics or organics. Wastes and discharges from these types of facilities could be listed or otherwise characteristically hazardous, if not listed, and thus likely candidates for waste minimization utilizing the invention disclosed herein.
The EPA identified the "listed" wastes, and by definition classified these wastes as hazardous without the need for ongoing analysis, after conducting detailed industry and process studies involving literature reviews, engineering analyses, surveys and questionnaires, site visits and waste sampling. Such listed wastes include K048, K049, K050, K051, K052, F037 and F038. The EPA places special emphasis on the hazardous constituents contained in specific wastes generated by the particular industry or process studied. See e.g. 55 FR 11798 and 40 CFR 261.11(a) (3), all of which are incorporated by reference. Through the listing process, the EPA engages in assessing information gathered for industries or processes with sufficient similarities in operations, raw materials input, final product configurations, and waste streams, such as the petroleum refining industry. The EPA's listing decisions for petroleum refinery waste streams from specific sources essentially hold that for some of the waste streams, the make-up of hazardous constituents that would likely exist in these streams would be relatively consistent among comparable facilities. Accordingly, the EPA deemed that sufficient information existed to predict that certain streams would usually be hazardous because of the constituents present in the typical streams, and thus the EPA "listed" these wastes. The EPA retained a "delisting" procedure, by which, any operator can prove that their specific waste, which is otherwise "listed," is so different that the specific stream should be taken off of the listed waste category for their stream at their facility. The EPA deals with de-listing requests on a case-by-case basis. Thus in most instances, listed wastes among various facilities, such as petroleum refineries, should be relatively comparable for each listing. For example, one would expect minimal variances between DAF and API Separator sludges at different petroleum oil refineries. These differences should still be minimal even if crude feedstocks or various operations in the refineries vary because the wastes just noted represent the end of the line oils and greases which are usually entrained in the wastewater phase of operations. The entrained or emulsified oil and greases, wash waters, and process area storm waters, which usually flow to the wastewater treatment systems, should not vary much between facilities, crude feed types, or ancillary processes. The EPA is concerned with the overall hazardous nature of all oil/water/separation sludges generated intentionally or incidentally from petroleum refinery and other operations regardless of the type of device used to separate the wastes from the wastewaters and regardless of where the treatment takes place. See e.g. 40 CFR 260.20, 260.22, 42 U.S.C. 6921(f), 55 FR 46354 and "Petitions to Delist Hazardous Waste: A Guidance Manual", 2nd edition, EPA 1993, all of which are incorporated by reference.
Following the Hazardous and Solid Waste Amendments of 1984, the EPA implemented a land disposal ban by promulgating Land Disposal Restrictions (LDRs) for many of the listed wastes, including for example, the DAF and API Separator sludges, effectively prohibiting the land disposal of specific wastes unless specific pretreatment criteria are met. See 40 C.F.R. 268 and 51 F.R. 40572, 52 F.R. 25760, 53 F.R. 31138 and 55 F.R. 22520, all of which are incorporated by reference. The specific pretreatment criteria are referred to as Best Demonstrated Available Technology (BDAT) standards.
The DAF unit and API Separator are commonly used in industry, and particularly the petroleum refining industry, for oil/water/sludge separation. The DAF incorporates mechanical separation of oil materials from water through the introduction of dispersed air. Oil containing sludges are removed and the remaining partially treated water flows onward for additional treatment. The DAF sludges require treatment and disposal as a hazardous waste. The API Separator is typically designed to allow waste-water containing oil and grease to flow by gravity and discharge through a lower outlet. The oil, with a density less than for water, floats on the surface and remains in the separator until removed by skimming or other method. Sludges are also generated from the API Separator, and these must usually be treated and disposed of as a hazardous waste.
In the waste treatment arena, there are several examples of systems which employ alternative approaches to traditional land treatment and methods for treating soils contaminated through years of land disposal/treatment of refinery wastes.
For example, U.S. Pat. No. 5,232,596 by Castaldi, illustrates a Bio-Slurry Reaction System and Process for Hazardous Waste Treatment. Castaldi introduces hydrocarbon contaminated sludges containing soils, requiring dissolving contaminants into an aqueous phase through forming of a slurry with solids and water, which after processing generates solids, including a biodegradation residue which requires further treatment for heavy metals recovery or stabilization and solidification before being sent to a treated waste landfill. Castaldi discloses a liquid/solids separator that partitions the bioreactor series output into three distinct layers, including mixed liquor bioslurry, a biodegraded waste residue, and a liquid decant layer. Also, Castaldi defines the microbiology of the process by disclosing the combined use of genus Pseudomonas in the family Pseudomonadaceae and Acinetobacter in the family Neisseriaceae in the form of activated sludge from petrochemical treatment bioprocesses and cosubstrates to effect at optimal temperatures and required residence times, the biodegradation of hazardous constituents in tarry-oily sludges and soils. Large populations of acclimated organisms are utilized according to Castaldi.
Castaldi also discloses a process and a system requiring a plurality of in-series reactors, with staged introduction of air and mixing, in a closed system which incorporates an off-gas system, including carbon dioxide removal, for recirculating gases generated from the process back to the bioreactors for further reaction and biodegradation of soils. The first stage bioreactor in the series is a waste dissolution reactor operated under anoxic conditions (dissolved oxygen concentration less than 0.5 mg/L). Significantly the following reactor stages are used to taper the load (waste to bacteria ratio) in order to achieve biotreatment. The methods and systems illustrated by Castaldi generate ongoing solids for further external treatment, including processing for heavy metals, and disposal. The waste illustrated for treatment under Castaldi is recovered from previously land farmed or land disposed waste or waste mixed with soils.
T. Oolman, F. J. Castaldi, G. P. Behrens and M. L. Owens of Radian Corporation in Austin, Tex. (hereinafter, "Radian I") published an article in the industry trade journal Hydrocarbon Processing entitled, "Biotreat Oily Refinery Waste" which discussed bench-scale treatability and economic feasibility study results and predictions for a tank-based biological treatment process for the treatment of oily refinery wastes. The key components of the process discussed in Radian I include 1) initial recovery of recyclable oil, 2) biological degradation of hazardous organic components, 3) chemical stabilization of metals, and 4) dewatering of the residual sludge. The Radian I authors highlight that pretreatment and post treatment steps are a significant part of the process; that the first step of the process includes oil-water-solids separation by centrifugation or filtration, allowing recovery of valuable product; that degradation of organic components in a bioslurry reactor and metals stabilization follow; and, that residual solids are dewatered and then disposed of off-site.
The Radian I authors note that RCRA BDAT standards are the primary criterion for technology selection and permitting issues are mentioned as factors affecting economic feasibility of an on-site treatment process. The Radian I authors specifically note that treatment of typical refinery sludges to BDAT standards does not imply that a big reduction in waste volume is necessary. Thus, the focus of the process discussed in Radian I is to treat to BDAT standards rather than to reduce solid waste volumes. The Radian I authors base their information on bench-scale treatability studies and the article focuses on technical and economic feasibility issues. The Radian I authors do not disclose information on how to start-up or operate a pilot or a full-scale treatment facility.
According to the Radian I authors, in order to achieve biotreatment, biotreatment assessments must be conducted in order to determine the optimum process configuration and operating conditions, noting from their experience that kinetics of a process and the ultimate fate of compounds may vary substantially with changes in waste characteristics and methods of processing. The Radian I authors do not disclose the bacteria used or any details of the microbiology. The Radian I authors state that they conducted bench scale treatability studies on three waste samples from a Gulf Coast refinery. The wastes referenced in Radian I include slop oil solids (K049), primary sludge (F037) and a mixture of API Separator sludge (K051) and DAF float (K048). The Radian I authors cite degradation of selected hazardous constituents and residual solids requiring further disposal in a RCRA-permitted landfill.
In another issue of Hydrocarbon Processing, a one-page Radian Corporation contribution appeared incorporating a comparable to the Radian I process flow diagram, descriptive summary and process economics description for a "bioslurry treatment of oily wastes" process (hereinafter, "Radian II"). Radian II does not disclose the bacteria utilized or any details of the microbiology and, like Radian I, relies on and anticipates land disposal as an integral step in the treatment process.
U.S. Pat. No. 5,271,845 discloses an Aerobic Biological Process for Treating Waste Sludges. This process requires heating of the sludge to induce acclimation of indigenous microbes and the release of extra-cellular enzymes.
U.S. Pat. No. 5,217,616 by Sanyal et al., discloses a Process and Apparatus for Removal of Organic Pollutants From Waste Water. Sanyal et al. discloses fixed or stationary biomass structures, with passages, various shapes and spacings, designed for fluid flow contact with various surfaces.
U.S. Pat. No. 5,286,386
discloses a Solvent Extraction Process for Treatment of Oily Substances, including sludges from petroleum refining operations, incorporating the addition of solvents, surfactants and flocculants, and teaching extraction.
U.S. Pat. No. 4,816,158, a Method for Treating Waste Water from a Catalytic Cracking Unit is disclosed. This process specifically addresses the treatment of a specific waste stream resulting from the catalytic cracking operation conducted in refineries. The treatment process disclosed functions as a batch rather than a continuous process. Also, the times allowed for aeration range between three to six hours and the maximum aeration time cannot exceed twelve hours. Various cycles of the batch operation are conducted intermittently, and solids must be removed.
U.S. Pat. No. 4,874,505 discloses a method for the Recycle of Oily Refinery Waste, effectively routing petroleum refinery sludges to a delayed coker unit where the combustible portions of the sludge are converted to petroleum coke and lower molecular weight liquid products are recovered.